在HTML中设定没做超链接的flash的链接

<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"
    codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=7,0,19,0"
    width="180" height="163">
    <param name="movie" value="Flash地址">
    <param name="quality" value="high">
    <param name="wmode" value="transparent">
    <param id="flashvars" name="flashvars" value="clickthru=http://www.sina.com">
    <embed src="Flash地址" width="180" height="163" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer"
        type="application/x-shockwave-flash" wmode="transparent"></embed>
</object>
这个时候点击flash可以跳到sina <object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"
    codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=7,0,19,0"
    width="180" height="163">
    <param name="movie" value="Flash地址">
    <param name="quality" value="high">
    <param name="wmode" value="transparent">
    <param id="flashvars" name="flashvars">
    <embed src="Flash地址" width="180" height="163" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer"
        type="application/x-shockwave-flash" wmode="transparent"></embed>
</object>
<script language="javascript">
var p = "clickthru=http://www.sina.com" ;
document.getElementById("flashvars").value = p;
</script>
现在却不行了，为什么呢？